A study on extracting thin sea ice area from space

Global warming is one of the most serious problems the earth is facing in the 21^st Century. In order to detect the sign of global warming, the importance of sea ice monitoring is increasing. Especially, sea ice thickness is an key parameter for understanding the heat flux of sea ice area. However, estimation of sea ice thickness with satellite remote sensing is not easy. In this study authors have examined the possibility of extracting thin sea ice area from remotely sensed data from space. The study was performed in the Sea of Okhotsk. Firstly, the possibility of estimating thin ice thickness with high resolution optical sensor RSI(IFOV=8m) on FORMOSAT-2 satellite was examined. The comparison of RSI data with in situ measurement of ice thickness suggested the possibility of estimating sea ice thickness with RSI data for less than 20 cm under the cloudless and snow free condition. The correlation between RSI data and MODIS data(IFOV=250m) was also examined for the thin ice area. The result also suggested the possibility of extracting thin sea ice area from MODIS data. Based on these results, the authors have examined possibility of extracting thin sea ice area with passive microwave sensor AMSR-E by using thin ice area estimated with MODIS data as truth data. Since the horizontal polarization of 19GHz are more sensitive to water than the vertical polarization of 19GHz, the authors have utilized the polarization difference of 19GHz for extracting thin sea ice area from AMSR-E data. The detailed study result will be presented in this paper.